Signal-transmission system



March 27, 1928.

R. B. MEYER ET AL SIGNAL TRANSMISSION SYSTEM Filed Do. 15, 1926 I I a l. C Yhaaz ATTORNEY Patented Mar. 27, 1928.

UNITED STATES PATENT OFFICE.

RAYMOND .B. MEYER AND LEO C. YOUNG, OF WASHINGTON, DISTRICT OF COLUMBIA,

ASSIGNOBS TO WIRED RADIO, INC., OF NEW YORK, N. Y., A. CORPORATION OF DELAWARE.

SIGNAL-TRANSMISSION SYSTEM.

Application filed December 15, 1926. Serial No. 155,072.

Our invention relates broadly to electron tube transmitters and more particularly to a circuit arrangement for a high frequency signal transmitter. I

One of the objects of our invention is to provide a circuit arrangement for an electron tube transmitter Which operates at rel atively high frequencies under piezo electric crystal control with means for maintamlng 1 the electron tubes in a condition of maximum operating efliciency at all times.

Another object of our invention is to provide a novel circuit arrangement for keying a high frequency signal transmission appa- 5 ratus by which the grid electrodes of the tubes are prevented from becoming charged at positive polarity. for any protracted period thereby preserving the life of the tubes.

Another object of our invention is to provide a bi-later circuit arrangement for the electron tubes of-a high frequency signal transmitter whereby the tubes may be operated from a power source of alternating currentfor the transmission of high frequency signals.- i

Another object of our invention is to pro- & vide a crystal controlled high frequency slgnal transmission system in which the crystal controlled oscillator is maintained in a condition of continuous oscillation while the signals are eifected by a change in condition in the power amplifier circuit.

Still another object of our .invention is to provide a balancedcircuit for a high frequency piezo electric crystal control transmission system the circuits of which are supplied with power from an alternating current source and in which the principle of frequencymultiplying is employed w th a 40 special circuit arrangement for obtaining the required high grid ditional negative grid otential for blocking the operation of the equency multiplying tubes in the production of signals.

Our invention will be more clearly understood from the specification hereinafter following by reference to the accompanying drawing which diagrammatically shows the circuit arrangement for the electron tube transmission system of our inventien.

Our invention is directed to a piece electric c stal controlled electron tube transm t ter w ich may be operated from a single source of altern ting current the frequency transformer so connected in the circuit that potential and the adof which may-vary over a wide rangeis uch as 25 to 1,000 cycles. The negative grid po tentials for the operation of the electron tubes are obtained in a unique manner The filament and plate potentials for the-LL several electron tubes are obtained by the} v 1 interposition oftransformers between the power source and the circuits of the e lectron tubes. The system of keying the electron tube transmitter is closely associated with a method of producing the grid poten- $5 tials for the several tubes. In the development of electron tubes transmitters we have endeavored to obtain negative grid poten tials for the operation of the tubes from a 7 0 when the plate of any given tube has a positlve potential impressed upon it the grid. of the same tube is subjected to a negative potential. It follows that when" the plate be comes negatively charged the grid has a positive potential impressed thereon. In electron tube transmitters of piezo e'lec'tric crystal control which employ the principle of frequency multiplying, the positive grid potentials are necessarily of a greater order of magnitude than those ordinarily required while the negative potentials necessary to completely block the grid for keying purposes arealso greater. In attempting to supply these potentials by means of atransformer it was found vthat after. a short periodof operation thefr'adio frequency. voutput of the tubes materially decreasedi vuntil a; I i I point was reached where oscillations ceased entirely. It was found that these tubes could be restored to operation by burning the filaments brightly for a protracted pee riod withino plate potential on the tubes. I

It was determined, therefore,ft'hat whenthe grids became highly positivetheeifectlwas 2955 to temporarily destroy the electron emission-:6 of.v the tubes. The transformer method! of supplying grid potentials, therefore, could not be used in sets of this type. v x

The circuit arrangement of ourv invention was developed with a view of avoidin the detrimental effects of positive potentia s on the grids. The circuit set forth in this application isso arranged that the grids are never subjected to positive potentials and we accordingly the continuous operation period of the tubes is prolonged. Ihe negative potential is increased for the blocking of the grids in the production of signals without undue arcing at the key contacts.

Referrin to the drawing in more detail reference aracters 1 and 2 designate the oscillator tubes, 3 and 4 indicate the frequency multiplier tubes and reference char- .acters 5 and 6 show. the power ampllfier tubes. The antenna is represented at 7 and the counterpoise is shown at 8; .The

tubes are connected in balanced relationship" throu hout the several circuits as represented. 'he oscillator tubes 1 and 2 have their input circuits connected with the piezo electric crystal element *9 positione between electrodes 10 and 11, the tubes 1 and 2 operating-to sustain the oscillations of the piezo, electric crystal element. The output circuits of the tubes -1 and 2 are coupled to the input circuits of the frequency multiplier tubes through the couplingfcircuit 12. The output circuits of the frequency multiplying tubes 3 and 4 connect through coupling circuit"-14 with the input circults of the power amplifier tube system at 6. The energy at increased amplitude is impressed on the antenna counter-poise system 78 through the coupling circuit 15. The filament transformer is designated at 16 as including primary winding 17 and secondary winding 18. The power supply line' from the alternating current source is brought in at terminals 19 and after passing through main switch 20 the fr winding the fr the power amplifier tubes ,5 and'6. The priis supplied to the primary windings ofthe several transformers. A circuit breaker 21 is interposed in the primary circuitfor the rotection of the system. -A transformer 22 aving secondary winding 23 and primary the oscillator tubes. The transformer 25 having secondary winding 26 and primary winding 27 supplies the plate circuits for equency multiplier tubes 3 and 4 and mary windings 24, 27 and 17 are all supplied from the power source connected at Connections are provided at 28 for measurements of the currents in various parts of the filament circuits.

IWe 'providea resistance, R whichis connected between the center or mid tap of the secondary winding 26 of transformer 25 and relay 29- from 'whence the circuit the keg procee s to the filament or ground throu h the ammeterA -When the contacts of t e key relay 29 .areclosed the plate circuits of equency multiplier and the amplifier tubes 3, 4, 5' and 6are completed and plate current flows. This results in a drop of potential over- R This resulting dlfierence in potential is applied to the grids of the tubes 3.an d 4 by means of the connections indicatedby30 and-31. It will be noted that the polarity of ments. By properly selecting the value of duees the necessary 24 supplies the plate potential for the potential applied to the grids is negative with respect to. the fila R the correct value of tained for best operating characterlstics.

R is a resistance connected between the mid tap of secondary transformer 22, supplying the potential for the master oscillator tubes 1 and 2, and fila- -ments or ground. This arrangement pronegative grid potential for these tubes. It will be noted that this circuit is not keyed and therefore the tubes are permitted to oscillate continuously, a feature that is necessary, or at least, highly desirable when quartz crystal control is em ployed. v I

The contacts of key relay 29 are controlled by winding 32 through a control line 33 When the key contacts are closed, the frequency multiplier 5 and 6 receive plate current and the proper grid potentials are automatically established. NOW, as the key contacts 29 are remagnitude that the grid blocks and plate current ceases to flow. This prevents arcing at the key contacts cient and clean cut key action. When the key contacts are actually separated theresistance inthe center lead is practically infinite and the negative potential (staticpotential). impressed on the grids equals in magnitude the voltage ondary of theQplate transformer 25 between the center tap of winding 26 and the extreme end. :The current which flows in the center tap is. uni-directional pulsating current thusthegrids are never subjected to posltlve potentials as in the case where transformers are. used to'supply grid po-" tenials. Another advantage of this system isthat as .plate current tends to increase,

the drop over the resistance R increases: with resulting increase in the negative potential applied to the grids whichin turn automatically regulates the plate current.

Hence it will be seen that there is estab:

potential may be obwinding 23 of the plate and amplifier. tubes 3, 4,

a greater negative p p open, thenegative potential on the grids has reached such a and resultsin efiideveloped in the sec- I lished an automatic" compensating action. for I limiting. plate current to desired Aline rela values.

a power switch indicated at 35.

. Our system of keying and the supplying of negative grid potential to the power amy H I 34i-s provided for the control of the operation'of the transformers through plifier tubes has proven highly satisfactory in operation, and although we have descrlbed the invention in a preferred embodiment we desire it to beunderstood that modifications may be made and equivalents employed without departing from the spirit of our invention.

What we claim as new and desire to secure by Letters Patent of the United States is as follows 1. A high frequency signal transmitter comprising a plurality of electron tubes each having grid, filament and plate electrodes, said tubes being connected for the generation of oscillations, the multiplication of the frequency of said oscillations and the increase in amplitude of the oscillations atmultiplied frequency, a power source of al ternating current, a transformer having pllmary and secondary windings with the primary winding thereof connected to said source and the secondary winding thereof arranged to impress high potential upon the plate circuits of said frequency multiplying tubes, a connection between a mid-point on said secondary winding to the filament electrodes of said frequency multiplying tubes, a high resistance interposed in said 7 connection,-a contact device located in sequency multiplying of said contact device.

ing a plurality of ries with said high resistance,-a connection between. the mid-point of said winding and the grid electrodes of said fretubes for establishing a negative potential on the grid electrodes of said frequency multiplying tubes, said negative potential increasing upon the opening -52. A-high frequency transmitter com riselectron tubes each aving grid, filament and plate electrodes said tubes being arranged pairs and connected in balanced relation, one pair of said tubes being arranged for the generation of high frequency oscillations said tubes being arranged to multiply the frequency of said oscillations while still another pair of said tubes is arranged for increasing the amplitude of said oscillationsat multiplied frequency, an alternating current power source, a transformer including primary and secondary windings with the primary winding thereof connected with said power source and the secondary winding thereof arranged to supply plate potential to saidfrequency miltiplymg tubes, a mid-tap connection for said secondary winding and a pair of circuits extending from said mid-tap connection, one of said circuits connecting to the grid electrodes of said secondary and another pair of" 1gb ne atrodes of said' frequency ,multipllying tubesmay be normally subjected to a tive potential and the negativepotential e- I creased for the production-of slgnals.

3. A high frequency signal transmission system comprising a plurality of electron tubes each having grid, filament and plate electrodes said tubes being arranged in pairs, one pair of said tubes generate'high frequency oscillations, another pair of said tubes operating to multiply the frequency of the oscillations generated by said first mentioned pair of electron tubes, and an additional pair of electron tubes operating to increase the amplitude of said oscillations at multiplied frequency, a power source of alternating current, a transformer having primary and secondary windings with the primary winding thereof connected with said source and the secondary winding -arranged to supply plate potential for the circuits of said frequency multiplying tubes and said amplifying'tubes, a mid-tap on said secondary winding,

tween said mid-tap and the grid electrodes of said frequency multiplying tubes and said .power amplifying tubes, a set of contacts interposed in said connection whereby a high negative potential may be normally impressed upon said grid electrodes and said negative potential decreased for the production of signals.

4. In an electron tube transmitter a circuit for generating high frequency oscillations, an electron tube frequency multiplier system connected with said circuit, an electron tube power amplifier system connected with said frequency multiplier system, grid, filament and plate electrodes for said electron 1 ondary windings said primary winding being connected with said source and said secondary winding having the mid-point thereof connected with the gridel ectrodes of said frequency multiplier and power amplifier tubes, a circuit including a high resistance and a set of contacts connected between said mid-tap and the filament electrodes of said frequency multiplier and powercamplifier tubes, said grid electrodes being normally subjected to a high negative potential when said contacts are open, said contacts operating when closed to effectively include said resistance between sai grid'and filament electrodes decreasing the negative potential on said electrodes for the production of signals, the potential on said plate electrodes being automatically regufrequency multiplying tubes and the othen lated in accordance with the voltage drop of saidcircuits being connected with the filament electrodes of said frequency multiplying tubes, said last mentioned circuit including a resistance and a set of contacts in series therewith whereby-the grid elec over said resistance.

In testimony whereof we aflix our signatures.

RAYMOND B. MEYER. LEO C. YOUNG.

operating to 

